System and Method for Molding Amorphous Polyether Ether Ketone

ABSTRACT

A method for molding amorphous polyether ether ketone including steps of preparing a molten mass including polyether ether ketone, cooling a mold assembly to a temperature of at most about 200° F., and injecting the molten mass into the cooled mold assembly.

FIELD

This application relates to polyether ether ketone and, moreparticularly, to amorphous polyether ether ketone and, even moreparticularly, to molding amorphous polyether ether ketone.

BACKGROUND

Aircraft experience electromagnetic effects (EME) from a variety ofsources, such as lightning strikes and precipitation static. Metallicaircraft structures are readily conductive and, therefore, arerelatively less susceptible to electromagnetic effects. Basicepoxy-based composite aircraft structures, however, do not readilyconduct away the significant electrical currents and electromagneticforces stemming from electromagnetic effects. Therefore, when compositesare used on an aircraft, steps are often taken to protect againstelectromagnetic effects, such as by incorporating conductive materialsinto the composites.

Fasteners with integral dielectric layers have been developed in anattempt to provide protection against electromagnetic effects. Forexample, U.S. Pat. Pub. No. 2013/0259604 discloses a fastener having afastener head and a layer of dielectric material mechanically attachedto the fastener head. The layer of dielectric material may include apolymeric material, such as polyether ether ketone.

Polyether ether ketone is commonly used in the aerospace industry due toits dielectric properties, its ability to maintain strength at elevatedtemperatures, and its chemical resistance. However, the limitedtoughness of polyether ether ketone has curtailed its application as adielectric material in connection with electromagneticeffects-protective fasteners.

Accordingly, those skilled in the art continue with research anddevelopment efforts in the field of electromagnetic effects protection.

SUMMARY

In one embodiment, the disclosed method for molding amorphous polyetherether ketone may include the steps of: (1) preparing a molten massincluding polyether ether ketone; (2) cooling a mold assembly to atemperature of at most about 200° F.; and (3) injecting the molten massinto the cooled mold assembly. The cooling and injecting steps may beperformed in series (e.g., cooling then injecting) or simultaneously(cooling while injecting).

In another embodiment, the disclosed system for molding amorphouspolyether ether ketone may include a mold assembly defining a cavity anda fluid channel, a cooling system in fluid communication with the fluidchannel, the cooling system supplying a cooling fluid to the fluidchannel, wherein the cooling fluid cools the mold assembly to at mostabout 200° F., and a polymer injection subsystem in fluid communicationwith the cavity, the polymer injection subsystem supplying a molten massto the cavity, wherein the molten mass includes polyether ether ketone.

In another embodiment, disclosed is part (e.g., a mechanical part for anaircraft) formed from the disclosed method for molding amorphouspolyether ether ketone and/or the disclosed system for molding amorphouspolyether ether ketone.

In yet another embodiment, disclosed is a fastener that includes afastener body and a portion of polyether ether ketone connected to thefastener body, wherein the polyether ether ketone has a crystallinity ofat most about 15 percent. For example, the fastener body may include ashaft and a head, and the polyether ether ketone may be connected to thehead.

Other embodiments of the disclosed system and method for moldingamorphous polyether ether ketone will become apparent from the followingdetailed description, the accompanying drawings and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of an electromagneticeffects-protective fastener formed in accordance with the disclosedsystem and method for molding amorphous polyether ether ketone;

FIG. 2 is a schematic representation of the disclosed system for moldingamorphous polyether ether ketone;

FIG. 3 is a flow diagram of the disclosed method for molding amorphouspolyether ether ketone;

FIG. 4 is a flow diagram of an aircraft manufacturing and servicemethodology; and

FIG. 5 is a block diagram of an aircraft.

DETAILED DESCRIPTION

Referring to FIG. 1, one embodiment of the disclosed electromagneticeffects-protective fastener, generally designated 100, may include afastener body 102 having a shaft 104 and a head 106 connected to theshaft 104. A portion 108 of amorphous polyether ether ketone may bemolded onto the fastener body 102. For example, the portion 108 ofamorphous polyether ether ketone may be molded onto the head 106 of thefastener body 102, thereby forming a layer 110 on the head 106, such ason the top of the head 106 (as shown in FIG. 1) and/or on the side ofthe head 106.

The fastener body 102 may be formed from various materials. As onegeneral, non-limiting example, the fastener body 102 may be formed froma metallic material. As one specific, non-limiting example, the fastenerbody 102 may be formed from titanium or titanium alloy. As anotherspecific, non-limiting example, the fastener body 102 may be formed fromaluminum or aluminum alloy. Furthermore, while a threaded bolt-typefastener is shown in the drawings, those skilled in the art willappreciate that various mechanical fasteners may be used withoutdeparting from the scope of the present disclosure.

Various engagement features 112 (e.g., undercut protrusions; a roughedsurface; etc.) may optionally be present on the head 106 to enhance theconnection between the top layer 110 and the head 106 of the fastenerbody 102. Additionally or alternatively, an optional tie layer (e.g., anadhesive) may be positioned between the top layer 110 and the head 106to enhance the connection therebetween.

While the fastener 100 is shown and described as having a portion 108 ofamorphous polyether ether ketone molded onto a fastener body 102,fasteners may be formed entirely of amorphous polyether ether ketonewithout departing from the scope of the present disclosure. Furthermore,those skilled in the art will appreciate that fasteners are only onespecific example of parts that may be formed from amorphous polyetherether ketone, in accordance with the present disclosure. Various otherparts, such as mechanical aircraft parts, may be molded from amorphouspolyether ether ketone using the disclosed system 200 and method 300.

As used herein, an “amorphous” polyether ether ketone refers topolyether ether ketone have a crystallinity that is substantially lessthan the crystallinity achieved using traditional polyether ethermolding techniques. In one expression, the amorphous polyether etherketone may have a crystallinity of at most about 15 percent. In anotherexpression, the amorphous polyether ether ketone may have acrystallinity of at most about 10 percent. In another expression, theamorphous polyether ether ketone may have a crystallinity of at mostabout 5 percent. In another expression, the amorphous polyether etherketone may have a crystallinity of at most about 2 percent. In anotherexpression, the amorphous polyether ether ketone may have acrystallinity of at most about 1 percent. In yet another expression, theamorphous polyether ether ketone may have a crystallinity of about 0percent.

Without being limited to any particular theory, it is presently believedthat molding an amorphous polyether ether ketone, as disclosed herein,results in the layer 110 of the electromagnetic effects-protectivefastener 100 having a greater toughness, as compared to a layer formedby molding crystalline (e.g., 30 to 35 percent crystallinity) polyetherether ketone using traditional molding techniques. The tougher amorphouspolyether ether ketone may result in the electromagneticeffects-protective fastener 100 being more suitable for use in aerospaceapplications, such as on an aircraft wing.

Referring to FIG. 2, one embodiment of the disclosed system for moldingamorphous polyether ether ketone, generally designated 200, may includea mold assembly 202, a polymer injection subsystem 204, and a coolingsubsystem 206. As is described in greater detail herein, the polymerinjection subsystem 204 may inject a molten mass of polyether etherketone (or a polyether ether ketone blend) into the mold assembly 202while the cooling subsystem 206 may cool the mold assembly 202, therebyyielding an amorphous polyether ether ketone.

The mold assembly 202 may include a first mold plate 208 and a secondmold plate 210. The first mold plate 208 may be sealingly, yetreleasably, mated with the second mold plate 210 to define a cavity 212therebetween. The first mold plate 208 may define a channel 214, and thechannel 214 may fluidly couple the cavity 212 with the polymer injectionsubsystem 204. While an axial configuration is shown, various moldconfigurations may be used without departing from the scope of thepresent disclosure.

A fastener body 102 (or other component) may be positioned in the moldassembly 202 to receive thereon the molded polyether ether ketone. Forexample, the second mold plate 210 may define a seat 215, and the head106 of the fastener body 102 may be seated in the seat 215 of the secondmold plate 210. Therefore, the head 106 of the fastener body 102 may atleast partially define the cavity 212 of the mold assembly 202.

The first mold plate 208, the second mold plate 210 or both the firstand second mold plates 208, 210 may define fluid channels 216. Thecooling subsystem 206 may direct a cooling fluid through the fluidchannels 216 to cool the mold assembly 202 to the desired temperature(e.g., prior to introduction of the molten mass). Cooling the moldassembly 202 may include cooling the entire mold assembly 202 or only aportion of the mold assembly 202 (e.g., only one of the first and secondmold plates 208, 210).

Without being limited to any particular theory, it is believed thatcooling the mold assembly 202 to a temperature of at most about 200°F.—which is a significant departure from standard polyether ether ketonemolding practices—may yield an amorphous (rather than crystalline)polyether ether ketone. In one realization, the mold assembly 202 may becooled to a temperature of at most about 150° F. In another realization,the mold assembly 202 may be cooled to a temperature of at most about100° F. In another realization, the mold assembly 202 may be cooled to atemperature ranging from about 50° F. to about 120° F. In yet anotherrealization, the mold assembly 202 may be cooled to a temperatureranging from about 80° F. to about 100° F.

Various cooling fluids may be used to cool the mold assembly 202 withoutdeparting from the scope of the present disclosure. In one variation,the cooling fluid flowing through the fluid channels 216 of the moldassembly 202 may be a liquid. Examples of suitable liquid cooling fluidsinclude, but are not limited to, water, alcohol and glycol. In anothervariation, the cooling fluid flowing through the fluid channels 216 ofthe mold assembly 202 may be a gas. Air (e.g., ambient air) is onenon-limiting example of a suitable gaseous cooling fluid.

Optionally, the mold assembly 202 (or select portions of the moldassembly 202) may be formed from (or may include) a highly thermallyconductive material, such as a highly thermally conductive metal (e.g.,copper). The highly thermally conductive material may aid in heattransfer.

The cooling subsystem 206 may be any apparatus or system capable ofsupplying a cooling fluid to the fluid channels 216 of the mold assembly202. For example, the cooling subsystem 206 may include a cooling fluidsource 220 and a pump 222 configured to pump the cooling fluid throughthe fluid channels 216 of the mold assembly 202, such as by way of fluidsupply lines 224. The cooling fluid may make a single pass through thefluid channels 216 of the mold assembly 202 or, alternatively, may berecirculated through the fluid channels 216.

In one particular implementation, a temperature sensor 226 may beconnected to the mold assembly 202 (e.g., to the second mold plate 210).Multiple temperature sensors, while not shown, may be used. Thetemperature sensor 226 may be in communication with the coolingsubsystem 206 (e.g., with a controller 228 associated with the coolingsubsystem 206). Therefore, the cooling subsystem 206 may activelycontrol the temperature of the mold assembly 202, such as by controllingthe temperature of the cooling fluid being supplied to the mold assembly202 (e.g., by way of a heat exchanger) and/or by controlling the flowrate of the cooling fluid being supplied to the mold assembly 202 tominimize a difference between a target mold assembly temperature and theactual temperature of the mold assembly 202.

The polymer injection subsystem 204 may be any apparatus or systemcapable of supplying a molten mass of polyether ether ketone (or apolyether ether ketone blend) to the mold assembly 202. The polymerinjection subsystem 204 may form the molten mass by heating thepolyether ether ketone to a temperature ranging from about 650° F. toabout 750° F., such as from about 670° F. to about 720° F. (e.g., about710° F.). Therefore, the molten mass of polyether ether ketone may beflowable as it passes to the mold assembly 202 and, ultimately, into thecavity 212.

In one construction, the polymer injection subsystem 204 may beconfigured as an injection molding machine, and may include a barrel230, a screw 232, a nozzle 234, a motor 236, one or more heaters 238,and a hopper 240 containing a quantity 242 of polyether ether ketone(e.g., pellets of polyether ether ketone). The screw 232 may be receivedin the barrel 230 and may be driven by the motor 236. Rotation of thescrew 232 within the barrel 230 may urge polyether ether ketonedeposited (from the hopper 240) proximate (at or near) the aft end 244of the barrel 230 to the forward end 246 of the barrel 230 and,ultimately, through the nozzle 234. As the polyether ether ketone movestoward the forward end 246 of the barrel 230, the heaters 238 may heatthe polyether ether ketone to form a molten mass. The polymer injectionsubsystem 204 may inject the molten mass of polyether ether ketone intothe mold assembly 202.

The molten polyether ether ketone injected into the mold assembly 202 bythe polymer injection subsystem 204 may enter the cavity 212 of the moldassembly 202 where it may be rapidly cooled to form the portion 108 ofamorphous polyether ether ketone on the head 106 of the fastener body102, as shown in FIG. 1. Because the mold assembly 202 is cooled, therate at which the molten polyether ether ketone is injected into themold assembly 202 (the injection rate) may be sufficiently high toensure the cavity 212 is properly and fully filled prior tosolidification of the polyether ether ketone. Those skilled in the artwill appreciate that the injection rate will depend on various factors,including the temperature of the mold assembly 202, the temperature ofthe molten mass of polyether ether ketone, the size of the cavity 212and the shape of the cavity 212.

Referring to FIG. 3, also disclosed is a method for molding amorphouspolyether ether ketone. One embodiment of the disclosed method,generally designated 300, may begin at Block 302 with the step ofpreparing a molten mass of polyether ether ketone (or a polyether etherketone blend). The molten mass of polyether ether ketone may be at atemperature ranging from about 650° F. to about 750° F., such as fromabout 670° F. to about 720° F. (e.g., about 710° F.).

At Block 304, a mold assembly may be provided. The mold assembly maydefine a cavity. For example, the mold assembly may include a first moldplate sealingly connected to a second mold plate to define a cavitytherebetween. A channel in one of the mold plates may provide fluidaccess to the cavity.

At Block 306, a fastener body may optionally be inserted into the moldassembly. For example, the fastener body may include a head and a shaft,and the head of the fastener body may be seated in a seat defined by oneof the mold plates forming the mold assembly. Therefore, together withthe first and second mold plates, the fastener body may at leastpartially define the cavity.

At Block 308, the mold assembly (including the fastener body, ifpresent) may be cooled. In one realization, the mold assembly may becooled to a temperature of at most about 200° F. In another realization,the mold assembly may be cooled to a temperature of at most about 150°F. In another realization, the mold assembly may be cooled to atemperature of at most about 100° F. In another realization, the moldassembly may be cooled to a temperature ranging from about 50° F. toabout 120° F. In yet another realization, the mold assembly may becooled to a temperature ranging from about 80° F. to about 100° F.

At Block 310, a sufficient quantity of the molten mass of polyetherether ketone may be injected into the cavity of the cooled moldassembly. For example, a screw rotating in a barrel may urge the moltenmass of polyether ether ketone into the cavity of the cooled moldassembly. The injection rate may be sufficiently high to ensure thecavity is quickly and fully filled with the polyether ether ketone priorto solidification of the polyether ether ketone.

Accordingly, by cooling the mold assembly prior to and/or duringinjection of molten polyether ether ketone, the disclosed system 200 andmethod 300 may yield amorphous (as opposed to crystalline) polyetherether ketone. The amorphous polyether ether ketone may have a highertoughness than crystalline polyether ether ketone and, therefore, may beused in more demanding applications, such as on aircraft.

Examples of the disclosure may be described in the context of anaircraft manufacturing and service method 400, as shown in FIG. 4, andan aircraft 402, as shown in FIG. 5. During pre-production, the aircraftmanufacturing and service method 400 may include specification anddesign 404 of the aircraft 402 and material procurement 406. Duringproduction, component/subassembly manufacturing 408 and systemintegration 410 of the aircraft 402 takes place. Thereafter, theaircraft 402 may go through certification and delivery 412 in order tobe placed in service 414. While in service by a customer, the aircraft402 is scheduled for routine maintenance and service 416, which may alsoinclude modification, reconfiguration, refurbishment and the like.

Each of the processes of method 400 may be performed or carried out by asystem integrator, a third party, and/or an operator (e.g., a customer).For the purposes of this description, a system integrator may includewithout limitation any number of aircraft manufacturers and major-systemsubcontractors; a third party may include without limitation any numberof venders, subcontractors, and suppliers; and an operator may be anairline, leasing company, military entity, service organization, and soon.

As shown in FIG. 5, the aircraft 402 produced by example method 400 mayinclude an airframe 418 with a plurality of systems 420 and an interior422. Examples of the plurality of systems 420 may include one or more ofa propulsion system 424, an electrical system 426, a hydraulic system428, and an environmental system 430. Any number of other systems may beincluded.

The disclosed system and method for molding amorphous polyether etherketone may be employed during any one or more of the stages of theaircraft manufacturing and service method 400. For example, componentsor subassemblies corresponding to component/subassembly manufacturing408, system integration 410, and or maintenance and service 416 may befabricated or manufactured using the disclosed system and method formolding amorphous polyether ether ketone. Also, one or more apparatusexamples, method examples, or a combination thereof may be utilizedduring component/subassembly manufacturing 408 and/or system integration410, for example, by substantially expediting assembly of or reducingthe cost of an aircraft 402, such as the airframe 418 and/or theinterior 422. Similarly, one or more of system examples, methodexamples, or a combination thereof may be utilized while the aircraft402 is in service, for example and without limitation, to maintenanceand service 416.

The disclosed system and method are described in the context of anaircraft; however, one of ordinary skill in the art will readilyrecognize that the disclosed service system may be utilized for avariety of different components for a variety of different types ofvehicles. For example, implementations of the embodiments describedherein may be implemented in any type of vehicle including, e.g.,helicopters, passenger ships, automobiles and the like.

Although various embodiments of the disclosed system and method formolding amorphous polyether ether ketone have been shown and described,modifications may occur to those skilled in the art upon reading thespecification. The present application includes such modifications andis limited only by the scope of the claims.

What is claimed is:
 1. A method for molding comprising: preparing a molten mass comprising polyether ether ketone; cooling a mold assembly to a temperature of at most about 200° F.; and injecting said molten mass into said cooled mold assembly.
 2. The method of claim 1 wherein said molten mass is at a temperature ranging from about 670° F. to about 720° F.
 3. The method of claim 1 wherein said molten mass consists essentially of said polyether ether ketone.
 4. The method of claim 1 wherein said mold assembly defines a cavity, and wherein said injecting step comprises injecting said molten mass into said cavity.
 5. The method of claim 1 wherein said cooling step comprises passing a cooling fluid through said mold assembly.
 6. The method of claim 5 wherein said cooling fluid comprises at least one of water, glycol and air.
 7. The method of claim 1 wherein said mold assembly is cooled to a temperature of at most about 150° F.
 8. The method of claim 1 wherein said mold assembly is cooled to a temperature ranging from about 50° F. to about 120° F.
 9. The method of claim 1 wherein said mold assembly is cooled to a temperature ranging from about 80° F. to about 100° F.
 10. The method of claim 1 further comprising the step of inserting a fastener body into said mold assembly prior to said injecting step.
 11. The method of claim 10 wherein said injecting step comprises contacting said fastener body with said molten mass.
 12. The method of claim 1 wherein said injecting step comprising rotating a screw within a barrel to establish a flow of said molten mass.
 13. A system for molding comprising: a mold assembly defining a cavity and a fluid channel; a cooling system in fluid communication with said fluid channel, said cooling system supplying a cooling fluid to said fluid channel, wherein said cooling fluid cools said mold assembly to at most about 200° F.; and a polymer injection subsystem in fluid communication with said cavity, said polymer injection subsystem supplying a molten mass to said cavity, said molten mass comprising polyether ether ketone.
 14. The system of claim 13 further comprising a fastener body positioned in said mold assembly, wherein said fastener body at least partially defines said cavity.
 15. The system of claim 13 wherein said cooling fluid cools said mold assembly to a temperature ranging from about 80° F. to about 100° F.
 16. A part formed from the method of claim
 1. 17. A fastener comprising: a fastener body; and a portion of polyether ether ketone connected to said fastener body, said polyether ether ketone having a crystallinity of at most about 15 percent.
 18. The fastener of claim 17 wherein said fastener body comprises a shaft and a head, and wherein said portion is connected to said head.
 19. The fastener of claim 17 wherein said polyether ether ketone has a crystallinity of at most about 10 percent.
 20. The fastener of claim 17 wherein said polyether ether ketone has a crystallinity of at most about 5 percent. 